Combine 4 cups water, salted as you would for pasta, and Grano in a pot. Bring to a boil, then reduce heat to medium. Simmer, stirring frequently, until Grano is tender but still chewy, about 30-35 minutes. Drain well.
When the Grano is almost cooked, drain the oil from the tuna into a 10-inch skillet. Add the olive oil, 1 tablespoon of the parsley, and the garlic and cook over medium heat, about 2 minutes. Add the pepper flakes and the cherry tomatoes, cover, and steam for 3 minutes.
Add the tuna, flaking it with a fork, then add the capers and cook, uncovered, for 1 minute more. Add the drained Grano and 1/4 cup of the cooking liquid and boil over high heat for 1 minute. Add the remaining parsley and salt and pepper to taste. Use a slotted spoon to divide servings on wide plates. Boil the pan juices down to napping consistency and pour over each serving. Serve at once.
Variation: Skillet Mussels with Grano
Omit the capers and tuna. Wash, soak, and clean 2 dozen mussels. Separately, steam open the mussels, shell, and add in with the pepper flakes.
Adapted from recipe by Paula Wolfert in Mediterranean Grains & Greens, 1998.